paper : 05 metabolism of lipids module: 07 types of lipids iii

1

Biochemistry METABOLISM OF LIPIDS

Types of Lipids

Paper : 05 Metabolism of Lipids

Module: 07 Types of Lipids III

Principal Investigator

Paper Coordinator and

Content Writer

Dr. Sunil Kumar Khare, Professor,

Department of Chemistry, IIT-Delhi

Dr. Suaib Luqman, Scientist (CSIR-CIMAP)

& Assistant Professor (AcSIR)

CSIR-CIMAP, Lucknow

Content Reviewer Prof. Prashant Mishra, Professor,

Department of Biochemical Engineering

and Biotechnology, IIT-Delhi

2


Types of Lipids

DESCRIPTION OF MODULE

Subject Name Biochemistry

Paper Name 05 Metabolism of Lipids

Module Name/Title 07 Types of Lipids III

Dr. Vijaya Khader Dr. MC Varadaraj

3


Types of Lipids

1. Objectives

To know about the complex lipids

What are the significance of glycolipids

How they act in a system

2. Concept Map

4


Types of Lipids

3. Description

3.1 Types of Lipids III

Complex Lipids

Glycolipids

In Mycobacteria LPS, Phosphatidylinositol dimannoside (lipoarabinomannan & lipomannan)

has been the anchoring domain and holds key significance in the interaction between host and

pathogen. This phosphatidylinositolglycans demonstrates the earliest version from prokaryotes

branded for cell surface protein anchoring and the lipoarabinomannan structural features have

been used across the globe as tuberculosis vaccine.

The surface of Leishmania, Entamoeba and Crithidia contains Lipophosphoglycan, a Glycolipid

serene with four domains: (1) an alkyl lyso phosphatidylinositol (2) core of glycan (3) Repeated

units of Gal-Man-PO4 backbone and (4) Cap structure of an oligosachharide has been involved

in a numerous functions inside the mammalian host.

In the strains of Streptococcus sp., Glucopyranosyl cardiolipin (Glycosylated cardiolipin) was

initially noticed and identified (18% of the lipid phosphorus) but present as a trifling constituent

in Vagococcus fluviatilis.

5


Types of Lipids

X = glucosyl residue

This infrequent glycolipid was also reported in Geobacillus steathermophilus (4% of total

phospholipids) acylated primarily by oleic acid (~ 25%) and palmitic acid (~ 33%). Revealed

predominantly as iso-C15:0 and anteiso-C17:0, this composite might be implicated in the

subvert effect of high temperature on the membrane organization and in the regulation of lipid

composition of G. stearothermophilus. In Deinococcus radiodurans, 3-(galactopyranosyl)-2-(3-

phosphatidyl) glyceroyl derivative, an exclusive glycophospholipid of a fatty alkylamine (~

33% of the total lipids) has also been identified.

The R3 (alkylamines) are generally straight chain compounds (C15-C17 or C16-C18), with

isomeric 17:1 bases preponderant.

A phosphocholine-containing glycoglycerolipid has been reported to be produced by

Mycoplasma fermentans in which the phosphocholine assembly is attached to the C6 of glucose

moiety. This lipid valor in the pathogenesis of rheumatoid arthritis by eliciting cell death or

inflammation through their phosphocholine dregs.

6


Types of Lipids

In Lactococcus and Streptococcus (Gram positive bacteria), a number of complex glycolipids

deriving from glucopyranosyl-1->2-glucopyranoside-diacylglycerol (kojibiosyl diacylglycerol

structure) were recognized.

(Acyl: fatty acyl group, Glcp: glycero-1-phospho, Ptd: 3-phosphatidyl)

In Staphylococcus membranes, additional complex phosphorylated compounds lipoteichoic

acids contains polymer of glycerol-1-phosphate allied to a glycosyl diglyceride or a

7


Types of Lipids

phosphatidyl glycosyl diglyceride is present. Other swapping on the glycerophosphate units

with alanyl or glycosyl groups has also been reported.

Structure of lipoteichoic acid from Bacillus subtilis where R1 and R2 are acyl group of fatty

acid and R3 is mainly acetylglucosaminyl, alanyl or H.

Sulfoglycoglycerolipids

Are lipids demeanoring a sulfur atom found in acidic membranes with a strong acidic pH (~2),

is present in some mammalian cells, chloroplast of higher plants, bacteria, algae and in fungi.

This type of lipid has also been described in Elakatothrix and Zygnema, green alga and in

Fucus, Pelvetia. At very low pH, carboxylic acids occur in unionized forms, but sulfolipids

subsist in the anionic form. In Chlorella, a new type of sulfolipid (sulfoquinovosyl

diacylglycerol: SQDG) derived from MGDG was discovered in 1959 at the Scripps Institute of

Oceanography (San Diego, CA, USA) which was afterward described in the thylakoid

membranes of all higher and lower plants. Hence, sulfolipids are present algae, cyanobacteria,

few basidiomycetes fungi (Clitocybe, Coprinus, Psalliota) and photosynthetic membranes of

plants,.

8


Types of Lipids

The biological function and mechanism for SQDG biosynthesis has been described in higher

plants predominantly under phosphate ravenous circumstances. SQDG is the lipid with a

sulfonic acid link, containing MGDG at C6 position of the monosaccharide unit,

sulfoquinovosyl (quinovose : 6-deoxy-D-glucose) is the sulfonoglucosidic moiety (6-desoxy-6-

sulfono-glucoside), R1 is often the palmitic acid and R2 is the unsaturated chain (16:3 n-3).

Heterosigma carterae (Raphidophyceae), a marine chloromonad was revealed to include a

intricate mixture of SQDG. The major fatty acyl groups contain 20:5 (n-3), 16:1 (n-3), 16:1 (n-

5), 16:1 (n-7) and 16:0. In Rhizobium meliloti, a symbiotic bacterium as well as in other strains

of Rhizobiaceae, existence of SQDG has been established. The occurrence of SQDG outside the

plant kingdom suggested the role of sulfolipid in the Rhizobium/legume relationship. In

Halobacterium, sulfate esters are reported with two alkyl diphytanylether chains. SQDG type

bearing mono-unsaturated (20:1 to 24:1) and saturated (14:0 to 24:0) fatty acids were also

extorted from a sea urchin (Scaphechinus mirabilis). Gustafson et al (1989) reported anti HIV-1

activity of SQDG from cyanobacteria containing linolenic and palmitic acids. Sulfate esters of

9


Types of Lipids

galactoglycerolipids are reported in quite a few mammalian tissues like brain, testis,

spermatozoa (3% of total lipids, >90% of total glycolipids in mammalian testis and ~0.3-1

mmole/g). The acyl groups R' and R'' are most frequently saturated (16/18 carbon atoms).

Seminolipids, mixture of alkylacyl and DAG is associated with myelination process of the

nervous system (Pieringer J et al., 1977, 166, 421). They are also essentail for mice

spermatogenesis. From Hyphomonas jannaschiana, a sea water bacterium, a tauroglycolipid has

been isolated lacking phospholipids. The structure determined as 1,2-diacyl-3-

glucuronopyranosyl-glycerol taurine-amide with 16:0, 16:1 n-7, 18:0, 18:1 n-7 and 19:0 as

major acyl chains.

i. Ceramides based Glycolipids:

Out of 150 known varieties in this cluster of glycosphingolipids, 50 categorized into the

structure of ganglio. Strewned mostly at the surface of the cell, they participate in the regulation

of cell interactions and dole out as distinctive markers for cells and mediate cell to cell detection

and contact. Ceramides based glycolipids are vital for the growth and development of organisms

10


Types of Lipids

and allude to viral or microbial infections and cancer. They form molecular complex named

‘Glycosynapse’ and helps in explicit recognition between cells function and signaling. They are

found in animals, bacteria, fungi, and plants. The grouping of glycosphingolipids is based on the

structure of the carbohydrate moiety and is as under:

Neutral glycosphingolipids (unsubstituted glycosyl group)

It includes single or extra glycosyl moieties, hexoses (sometimes pentose) and an added

hexosamine. As per the presence of glycosyl units they may be one glycosyl unit

(monoglycosylceramides), more than one glycosyl units (oligoglycosylceramidest) or

other structure containing only one glycosylated sphingoid base (deacylated

glycosphingolipids), one fatty acid linked to cerebrosides (acylated glycosphingolipids),

complex sphingolipids with a ceramide containing a cyclopropane chain and prenylated

residues on galactose (plakosides).

Acidic glycosphingolipids

Are zwitterionic molecules with glycosyl and carboxyl group, sulfate or phosphate.

Examples are gangliosides (a carboxyl group on sialic acid and several glysosyl

residues), acidic monoglycosylceramides, phosphonoglycosphingolipids,

sulfosphingolipids (ceramide di & tri hexosyl sulfate with one sulfate moeity on the

glycosyl unit, sulfatides), phosphosphingolipids (phosphorylceramide with

oligosaccharide or glycosyl head moeity).

ii. Lipopolysaccharides (LPS)

11


Types of Lipids

Are the endotoxin (endotoxic-o-antigens) emanated from the cell walls of Gram negative

bacteria and in a fungus (Antrodia camphorata). Due to their nature, they may cause numerous

pathophysiological symptoms like blood pressure decrease, diarrhea, fever, septic shock and

death. There are three parts in LPS, part A (Lipid A) silhouette a composite with part B

(polysaccharide core) through a glycosidic linkage which is allied to an external area of part C

(an immunogenic and capricious polysaccharide chain or antigen composed up of repeating

oligosaccharide units liable for the specificity of bacterial serological strain. Part A (Lipid A)

includes a backbone of b 1, 6-glucosaminylglucosamine with two phosphoester moiety at

position 1 of glucosamine I and in position 4 of glucosamine II. The position 3 of glucosamine

II assembles the glycosidic linkage (acid labile) to the polysaccharide chain. In E. coli, the

supplementary groups are replaced with fatty acids ((hydroxylated) as hydroxymyristate (two

amide & two ester linked) and laurate (fatty acid). In the same species, the LPS fatty acid

profiles vary distinctly from the phospholipids.

Structure of lipid A of Escherichia coli

12


Types of Lipids

3-hydroxyalkanoic acids and 2-hydroxyalkanoic acids are common hydroxylated fatty acids but

some bacteria (Achromobacter, Bacteroides, Brucella, Gardnerella, Sorangium, Thermus,

Thiobacillus) lacks hydroxy acids. Even carbon compounds (12-18 atoms) containing hydroxy

acids are straight-chain while odd-carbon acids are minor components (13-17 atoms) of

Bordetella, Pseudomonads, Pectinatus, Selenomonas, Vibrio and Veillonella. In

Capnocytophaga, Flavobacterium, Desulfovibrio, Legionella, Pseudomonas and Moraxella,

species a specialized branched chain hydroxy fatty acids (3OH i 11:0 up to3OH i 17:0) has also

been reported. In Pseudomonas and Azospirillum species, a small number of unsaturated

hydroxy fatty acids have been depicted, except the presence of 2OH, 18:1.

Listeria monocytogenes, an infective agent in milk, is the solitary Gram positive bacteria that

acquire LPS where the polysaccharide is non-toxic and the toxic activity is attributed to the part

A (Lipid A) that causes septic shock. The subsistence of LPS was established in a fungus

(Antrodia camphorate) of Polyporaceae family revealing fucose, glucose, galactose and sorbitol

in LPS, galactosamine and glucosamine were deficient. Furthermore, the sequestered compound

showed some anti-inflammatory effect and a low cytotoxicity. An efficient method using hot

ammonium isobutyrate solvent for the extraction of LPS and sequestration of lipid A from

bacteria has been described. Lipid X a closely related precursor of lipid A has also been

portrayed revealing various pharmacological properties.

iv. Sterol based Glycolipids:

13


Types of Lipids

They occur as free sterols, esters (acylated), alkyl ethers (alkylated), sulfated or linked to a

steryl glycoside moiety. The biosynthesis of sterol is everpresent amid eukaryotes but almost

wholly deficient in prokaryotes. Being absent in Archaea, they are sparingly distributed in

bacteria and Methylococcus capsulatus (proteobacterium), Gemmata obscuriglobus

(planctomycete) along with myxobacteria members. As a consequence, the existence of varied

steranes (saturated 4 cycle skeleton) in primordial rocks is used as proof for eukaryotic

evolution somewhere 2.7 billion years ago.

Structure of sterols with carbon numbers

The sterols have hopanoids as precursor and an oxygen-dependent biosynthesis starting with the

creation of 2, 3-oxidosqualene (primary intermediate). Hence, steroid and triterpenoid

hydrocarbon detection in the history of Earth has been used to surmise the relic of oxygenic

photosynthesis. It has been conjecture that levels of oxygen increased in the atmosphere made

the sterols evolution feasible and make possible the eukaryotes birth giving them with an

untimely protection mechanism against oxygen.

14


Types of Lipids

Free Sterols

Sterols (Greek: stereos-solid) shape an imperative cluster amid steroids. The unsaturated

steroids involve a 3-hydroxyl group (cholestane skeleton) and carbon atoms (8 or more) of an

aliphatic side chain at position 17 figuring the group of sterols. Being saponification resistant,

they are endowed in all animal and vegetal tissues important in the appraisal of marine sediment

maturity as a biological marker compound, yet past hundreds millions years. They also

comprise 3-hydroxysteroids (C27 to C30) crystalline alcohols and are classed as triterpenes

(being derived from squalene) directly by unsaturation, cyclization and 3-hydroxylation,

cycloartenol in plants or lanosterol in animals.

5cholestane

4. Summary

In this lecture we learnt about:

The Types of Glycolipids

Their benefit & advantages

paper : 05 metabolism of lipids module: 07 types of lipids iii

Documents